Method and system for processing semiconductor wafers

ABSTRACT

A method for processing semiconductor wafers includes processing a semiconductor wafer in a processing chamber having upper and lower chambers, decoupling the upper chamber from the lower chamber, cleaning the upper chamber, determining, while decoupled, that a leak rate and a particle count for the upper chamber meets predetermined criteria, and coupling the upper chamber to the lower chamber.

This application claims priority under 35 USC §119(e)(1) of provisionalapplication No. 60/226,365 filed Aug. 18, 2000.

TECHNICAL FIELD OF THE INVENTION

This invention relates generally to the field of semiconductors and,more specifically, to a method and system for processing semiconductorwafers.

BACKGROUND OF THE INVENTION

Many fabrication techniques are used for processing semiconductorwafers. One such fabrication technique is plasma etching. The plasmaetch process is usually performed in a processing chamber. There aremany requirements for processing chambers used for plasma etching andother semiconductor wafer fabrication processes. For example, it isimportant that vacuum leak rates and particle counts be at, or within,certain levels. Furthermore, processing chambers used for semiconductorwafer processing usually need to be cleaned after they are used.Therefore, semiconductor fabricators strive to process semiconductorwafers at low cost and in a fast and efficient manner.

One way of preparing processing chambers for use is to disassemble themand clean all the parts with a solvent such as alcohol. The processingchamber is then reassembled, coupled to a lower chamber that houses theprocessing equipment, and then a vacuum is pulled on the processingchamber. Leak rates and particle counts can then be measured to see ifthey are within acceptable levels. If they are not within acceptablelevels, then the processing chamber is taken off the lower chamber andcleaned further. This wastes considerable time and manpower. Another wayof cleaning processing chambers is to outgas them in an oven using, forexample, a nitrogen gas. Once again, the processing chamber is placed onthe lower chamber and the testing of the leak rates and particle countsis performed as described above. What is needed is a method or system toensure a preconditioned processing chamber before the processing chamberis set up on the lower chamber before being used for processingsemiconductor wafers.

SUMMARY OF THE INVENTION

The challenges in the field of semiconductors continue to increase withdemands for more and better techniques having greater flexibility andadaptability. Therefore, a need has arisen for a new method and systemfor processing semiconductor wafers.

In accordance with the present invention, a method and system forprocessing semiconductor wafers is provided that addresses disadvantagesand problems associated with previously developed methods and systems.

A method for processing semiconductor wafers includes processing asemiconductor wafer in a processing chamber having upper and lowerchambers, decoupling the upper chamber from the lower chamber, cleaningthe upper chamber, determining, while decoupled, that a leak rate and aparticle count for the upper chamber meets predetermined criteria, andcoupling the upper chamber to the lower chamber.

A mobile system for preconditioning a semiconductor processing chamberhaving an upper chamber and a lower chamber includes a mobile cart, ahot gas recirculating system coupled to the mobile cart and adapted tocouple to the upper chamber, a vacuum source coupled to the cart andadapted to couple to the upper chamber, a leak rate testing sourcecoupled to the cart and adapted to couple to the upper chamber, and aparticle count testing source coupled to the cart and adapted to coupleto the upper chamber.

Embodiments of the invention provide numerous technical advantages. Forexample, a technical advantage of one embodiment of the presentinvention is that there is a reduction in time from when a semiconductorwafer is processed to preconditioning a processing chamber for the nextprocessing cycle. Another technical advantage of one embodiment of thepresent invention is the reduction of processing variables such asprocessing chamber vacuum leak rates and processing chamber particlecounts. Utilizing one embodiment of the present invention results in aprocessing chamber being ready for use as soon as one processing cycleis finished using another preconditioned processing chamber. Thepreconditioned processing chamber is held under vacuum and the leakrates and particle counts are already known; therefore, the processingchamber just needs to be set up and used. Other technical advantages arereadily apparent to one skilled in the art from the following figures,descriptions, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the invention, and for furtherfeatures and advantages, reference is now made to the followingdescription, taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is an elevation view of one embodiment of a processing chamberhaving upper and lower chambers for processing semiconductor wafers inaccordance with the present invention;

FIG. 2 is a flowchart demonstrating one method of processingsemiconductor wafers in accordance with the present invention; and

FIG. 3 is an elevation view of one embodiment of a mobile cart forpreconditioning an upper chamber of a processing chamber in accordancewith the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Embodiments of the present invention and their advantages are bestunderstood by referring now to FIGS. 1 through 3 of the drawings, inwhich like numerals refer to like parts.

FIG. 1 is an elevation view of a processing chamber 100 having an upperchamber 102 and a lower chamber 104 for processing semiconductor wafers106. One example of processing chamber 100 is the Silicon Etch DPS PlusCentura™ from Applied Materials™. However, other types of processingchambers can be used for many different types of semiconductor waferprocesses. One example of such a semiconductor wafer process is plasmaetching.

In one embodiment, semiconductor wafers 106 are housed in upper chamber102, which is where the plasma etch process, or other semiconductorwafer process, is accomplished. Lower chamber 104 is the portion ofprocessing chamber 100 where processing variables, such as pressure,temperature, and RF frequency are produced and/or delivered to upperchamber 102. Since semiconductor wafer processing requires a cleanatmosphere, upper chamber 102 needs to be preconditioned before use.Therefore, upper chamber needs to be cleaned periodically, such as aftera plasma etch process. Since this normally requires disassembly, removaland/or replacement of parts, cleaning, and reassembly, then significanttime is wasted in processing semiconductor wafers. Not only is timewasted, but extra manpower may be required to precondition theseprocessing chambers, thereby wasting additional money and hurtingefficiency. Thus, a method of processing semiconductor wafers that isfast and efficient and done at low cost is desired. One such method isshown in FIG. 2.

FIG. 2 is a flowchart illustrating one method for processingsemiconductor wafers in accordance with the present invention. Asemiconductor wafer 106 is processed in processing chamber 100 havingupper chamber 102 and lower chamber 104 at step 200. As described above,this process could be a plasma etch process to, for example, etchpolysilicon or metal. After processing semiconductor wafer 106, upperchamber 102 needs to be cleaned. Therefore, upper chamber 102 isdecoupled from lower chamber 104 at step 202, and upper chamber 102 iscleaned at step 204.

There are many ways to clean upper chamber 102. For example, upperchamber 102 can be cleaned with a hot gas recirculating system (“HGRS”)301 as shown in FIG. 3, which is well known in the art of semiconductorwafer processing. In one embodiment, HGRS 301 is coupled to a cart 300,which is described in detail below, for the efficient and cost-effectiveprocessing of semiconductor wafers. Upper chamber 102 may also becleaned by outgassing in an oven or by disassembling and cleaning thevarious parts of upper chamber 102 with a solvent such as alcohol.

After cleaning upper chamber 102 at step 204, upper chamber 102 isreassembled, if necessary, and preconditioned. This preconditioninginvolves determining, while upper chamber 102 is decoupled from lowerchamber 104, that certain atmospheric conditions such as a leak rate anda particle count meet certain predetermined criteria, as indicated bybox 206. Leak rates and particle counts are important parameters whenprocessing semiconductor wafers 106. Leak rates and particle counts needto be at, or within, certain levels before semiconductor wafers 106 areprocessed. In one embodiment, the leak rate is a maximum of onemillitorr, and the particle count is a maximum of ten particles perminute. After the leak rate and the particle count reach predeterminedlevels, then upper chamber 102 is coupled to lower chamber 104 at step208. Processing chamber 100 is then ready to process semiconductorwafers without having to check the leak rate and the particle count.

Preconditioning upper chamber 102 while decoupled from lower chamber 104saves considerable time and manpower, as compared to conventionaltechniques, when processing semiconductor wafers. For example, if theleak rate and particle count are not known when upper chamber 102 iscoupled to lower chamber 104, then the leak rate and particle count haveto be checked after processing chamber 100 is put under a vacuum. If theleak rate and/or particle count is not at its predetermined value, thenupper chamber 102 is reconditioned again before being coupled to lowerchamber 104. The vacuum and testing procedures are performed again tomake sure processing chamber 100 is ready for processing semiconductorwafers. The reconditioning of processing chamber 100 may entail cleaningupper chamber 102 again, such as with HGRS 301, thereby consumingadditional time. As described above, HGRS 301 may be coupled to cart300. One example of such a cart is shown in FIG. 3.

FIG. 3 is an elevation view of a cart 300 for preconditioning upperchamber 102 in accordance with one embodiment of the present invention.Cart 300 includes a base 302 and a support plate 304 coupled to base 302that is operable to support upper chamber 102 of processing chamber 100.Cart 300 also includes HGRS 301 coupled to base 302 and adapted tocouple to upper chamber 102, a vacuum source 319 adapted to couple toupper chamber 102, a leak rate testing source adapted to couple to upperchamber 102, and a particle count testing source 321 adapted to coupleto upper chamber 102. Cart 300 may also include a vibration isolationsystem 312 disposed between base 302 and support plate 304.

Base 302 may be formed from any type of material and in anyconfiguration suitable for supporting support plate 304, upper chamber102, and additional desired equipment. Base 302 may have wheels 316, asshown in FIG. 2, to allow cart 300 to be mobile, and base 302 may havehandles 314 for easy handling and transportation of cart 300. Base 302may also have a cover 320 for protection of upper chamber 102.

Support plate 304 supports upper chamber 102 and may be formed from anytype of material and in any configuration suitable for supporting upperchamber 102. In one embodiment, support plate 304 is made of aluminum.Support plate 304 may also include a heating system 318, which is usedto heat upper chamber 102 to a desired temperature. This temperature maybe desired for such things as alignment purposes when coupling upperchamber 102 to lower chamber 104, or for processing purposes so thatupper chamber 102 is ready for processing semiconductor wafers 106 at,or near, its operating temperature, thus reducing processing time.

HGRS 301, as described above, is well known in the art of semiconductorwafer processing. In the embodiment shown in FIG. 3, HGRS 301 is coupledto base 302 and adapted to couple to upper chamber 102. HGRS 301 cleansupper chamber 102 to prepare upper chamber 102 for its next processingcycle. In one embodiment, HGRS 301 includes inlet valve 306, inletbellows 307, riser 308, outlet bellows 309, and outlet valve 310, whichwork together to cycle purge gas through upper chamber 102 as shown byarrow 350. In one embodiment, the gas is a nitrogen gas that is heatedto a temperature of approximately 130° C.; however, other types of gasmay be used as well as other temperatures. HGRS 301 may also includeother equipment to cycle purge gas through upper chamber 102.

Vacuum source 319 may be any type of vacuum source that is adapted tocouple to upper chamber 102. Vacuum source 319 may or may not be coupledto cart 300. Vacuum source 319 may hold upper chamber 102 under avacuum, or other desired pressure, for any period of time desired. Onceupper chamber 102 is placed under a vacuum, or other desired pressure,upper chamber 102 may then be checked for its leak rate and particlecount using leak rate testing source 320 and particle count testingsource 321.

Leak rate testing source 320 may be any type of leak rate testing sourceadapted to couple to upper chamber 102. Leak rate testing source 320 mayor may not be coupled to cart 300. Leak rate testing source 320 is usedto test upper chamber 102 for a desired value of vacuum leak rate. Inone embodiment, the leak rate is a maximum of one millitorr.

Particle count testing source 321 may be any type of particle counttesting source adapted to couple to upper chamber 102. In oneembodiment, particle count testing source 321 is an in situ particlemonitor from HYT, which is well known in the art of semiconductorprocessing. Particle count testing source 321 may or may not be coupledto cart 300 and is used to test upper chamber 102 for a desired particlecount. In one embodiment, the particle count is a maximum of tenparticles per minute.

Vibration isolation system 312 may be any type of vibration isolationsystem suitable for isolating support plate 304 from vibrationsemanating from base 302 or the environment. In one embodiment, vibrationisolation system 312 comprises rubber members.

Once the leak rate and the particle count of upper chamber 102 reachdesired values, upper chamber 102 may then be held under a vacuum untilready for the next processing cycle. This preconditioning allowsconsiderable savings in semiconductor wafer processing time by having aprepared processing chamber, with a known leak rate and a known particlecount, ready for substantially immediate use.

In operation, one embodiment of the present invention includesprocessing chamber 100 processing semiconductor wafers 106. After theprocess is performed, semiconductor wafers 106 are then removed. Upperchamber 102 is then decoupled from lower chamber 104 so upper chamber102 may be cleaned. Upper chamber 102 may be placed on support plate 304of cart 300, and HGRS 301 may circulate hot nitrogen gas to upperchamber 102 to precondition upper chamber 102 for the next processingcycle. After HGRS 301 cycle purges hot nitrogen gas through upperchamber 102, HGRS 301 is shut down and a vacuum is pulled on upperchamber 102. Then the leak rate and particle count of upper chamber 102are checked with leak rate testing source 320 and particle count testingsource 321 until predetermined values are reached. These predeterminedvalues depend on the process for which upper chamber 102 is to be used.Once these predetermined values are reached, upper chamber 102 is heldunder the vacuum until ready for use. Cart 300, if it has wheels such aswheels 316, may be moved from location to location depending on wherethe next processing system takes place. For example, cart 300 mayreceive upper chamber 102 after upper chamber 102 is finished processingsemiconductor wafers 106, then moved to a preconditioning station, andthen moved to the next processing station. Preconditioning upper chamber102 using mobile cart 300 allows for less downtime associated with theprocessing of semiconductor wafers.

Although embodiments of the invention and their advantages are describedin detail, a person skilled in the art could make various alternations,additions, and omissions without departing from the spirit and scope ofthe present invention as defined by the appended claims.

What is claimed is:
 1. A method for processing semiconductor wafers,comprising: processing a semiconductor wafer in a processing chamberhaving upper and lower chambers, wherein the upper chamber houses thesemiconductor wafer and the lower chamber comprises processing equipmentoperable to process the semiconductor wafer; decoupling the upperchamber from the lower chamber; cleaning the upper chamber; determining,while decoupled, that a leak rate and a particle count for the upperchamber meets predetermined criteria; and coupling the upper chamber tothe lower chamber.
 2. The method of claim 1, further comprising placingthe upper chamber under a vacuum.
 3. The method of claim 1, wherein theleak rate is a maximum of one millitorr per minute.
 4. The method ofclaim 1, wherein the particle count is a maximum of ten particles perminute.
 5. The method of claim 1, wherein cleaning the upper chambercomprises cycle purging hot gas through the upper chamber with a hot gasrecirculating system.
 6. The method of claim 5, and further comprisingcoupling the hot gas recirculating system to a mobile cart, and whereinthe hot gas is nitrogen.
 7. The method of claim 6, and furthercomprising: coupling a vacuum source to the mobile cart and operativelycoupling the vacuum source to the upper chamber; coupling a leak ratetesting source to the mobile cart and operatively coupling the leak ratetesting source to the upper chamber; and coupling a particle counttesting source to the mobile cart and operatively coupling the particlecount testing source to the upper chamber.
 8. The method of claim 1,further comprising holding the upper chamber under a vacuum until theupper chamber is coupled to the lower chamber.
 9. The method of claim 1,wherein processing at least one semiconductor wafer in a processingchamber comprises plasma etching.
 10. A method for preconditioning asemiconductor processing chamber, comprising: decoupling an upperchamber from a lower chamber, the upper chamber and lower chamberforming the semiconductor processing chamber when coupled together;placing the upper chamber under a vacuum; cycle purging hot nitrogen gasthrough the upper chamber with a hot gas recirculating system;determining that a leak rate and a particle count for the upper chambermeet predetermined criteria; and coupling the upper chamber to the lowerchamber.
 11. The method of claim 10, wherein the leak rate is a maximumof one millitorr per minute.
 12. The method of claim 10, wherein theparticle count is a maximum of ten particles per minute.
 13. The methodof claim 10, wherein cycle purging hot nitrogen gas through the upperchamber with a hot gas recirculating system comprises coupling the hotgas recirculating system to a mobile cart.
 14. The method of claim 13,and further comprising: coupling a vacuum source to the mobile cart andoperatively coupling the vacuum source to the upper chamber; coupling aleak rate testing source to the mobile cart and operatively coupling theleak rate testing source to the upper chamber; and coupling a particlecount testing source to the mobile cart and operatively coupling theparticle count testing source to the upper chamber.
 15. The method ofclaim 10, further comprising holding the upper chamber under a vacuumuntil the upper chamber is coupled to the lower chamber.